Field of the Invention
The invention relates to a tool and a method for machining fiber-reinforced materials.
Description of Related Art
In particular, the invention relates to the machining of fiber-reinforced composite materials, that is, such that consist of a composite of various materials, among these at least one fiber material. This relates in particular to fiber-reinforced, e.g. carbon fiber-reinforced, materials with a matrix, e.g. a plastic matrix (CFRP) or a carbon matrix (CFC).
Such materials are used in particular in lightweight construction because, despite weighing little, they are very strong. Accordingly, applications of fiber-reinforced materials are known in automotive construction, for sports materials, in medical technology, wind power, space flight, etc., in particular, however, in the aviation industry.
In this case the fiber-reinforced materials are often part of a sandwich material consisting of a plurality of individual layers, among these not only layers made out of fiber composites, but also metal layers made, in particular, out of aluminum alloys or titanium alloys.
The machining of such materials makes exceptionally high demands on cutting tools. Due to the considerable abrasiveness of the fibers, conventional cutting tools have only short service lives here. Particular problems become apparent during drilling when delamination or fraying of the drilling hole frequently occurs.
It is known to provide cutting tools with a diamond cutting edge. Known on the one hand are conventional diamond tools (PCD=polycrystalline diamond) with diamond inserts soldered onto the cutting edge. Further, even tools with complex tool geometries can be protected by means of the subsequent application of a diamond layer in the CVD (Chemical Vapor Deposition) process.
In WO 00/60137 a tool and a manufacturing method for this are described. A tool substrate is first pre-treated and provided with a diamond coating with two layers, which both have predominantly carbon in a diamond structure, in a CVD coating plant according to the hot-filament process, the first layer having a higher diamond content than the second layer. The coefficient of thermal expansion of the first layer is less than that of the substrate, and the coefficient of thermal expansion of the second layer is greater than the coefficient of thermal expansion of the first layer, in order to prevent cracks.